The general goal of this program remains the evaluation and validation of clinical cardiac transplantation as a therapeutic procedure. The specific scientific objectives incorporated in the program are directed toward development and refinement of techniques to maximize post-operative survival. They include: 1) refinement of clinical criteria for the selection of potential cardiac recipients most likely to achieve rehabilitation after operation, and assessment of the impact of clinical, physiological, and psychosocial factors present preoperatively on recipient survival and rehabilitation; 2) correlation of histocompatibility typing and recipient immunological responsiveness with postoperative rejection history and survival; 3) the definition of techniques for postoperative assessment of host immune responses, diagnosis and predictive grading of acute graft rejection by direct histological assessment with transvenous endomyocardial biopsy, and correlation of kinetic data relating to treatment with rabbit antihuman antithymocyte globulin with time of onset, frequency and severity of post-operative graft rejection; 4) identification and management of psychological and social stresses associated with transplantation; and 5) definition of functional and electrophysiological properties of the transplanted human heart, responses to various pharmacological and physiological interventions, and evaluation of the physiological and pathoanatomical changes associated with late postoperative complications such as graft arteriosclerosis. In addition, the clinic heart transplantation program constitutes a demonstration project in heart transplantation on both national and international levels. It furthermore provides in-depth training to both medical and surgical trainees in clinical and investigational aspects of this form of organ transplantation.